tablished, two cylinders from each of two batches during each shift will be made and cured as provided above. One pair of cylinders consisting of one cylinder from each of two different batches will be tested at the end of the curing period and must show the minimum curing strength required in order to stop curing of the pipe. If, for any reason, the strength of either test cylinder is less than that required, curing shall be continued and the remaining pair of cylinders tested after sufficient additional curing to insure the minimum curing strength requirement. If the second pair of test cylinders does not meet the strength requirement, curing shall be continued for such additional time, as determined necessary by the contracting officer, to insure the minimum curing strength requirement. All cylinders will be tested as soon as possible after removal from curing while still in the moist condition. Test cylinders shall be protected from temperatures below 40° F before, during and after curing operations. Pipe shall be protected from temperatures below 40° F before and during operations. (a) Steam curing.-Immediately after the pipe has been cast, it shall be enclosed within a suitable steam-curing chamber or enclosure that will protect the pipe from outside drafts and excessive loss of steam. Enclosures shall allow full circulation of thoroughly saturated steam around the inside and outside of the pipe, and the curing shall produce continuously moist surfaces of unformed concrete throughout the curing process. The ambient temperature rise within the enclosure shall not exceed 30° F per hour. The ambient temperature within the enclosure shall not exceed 100° F within 2 hours after mixing; thereafter, the temperature shall be brought to 130° F within a period of 2 hours and maintained between 130° and 150° F until the specified curing strength is attained. The temperature within the steam-curing chamber shall be thermostatically controlled and temperatures shall be recorded on a continuous recording chart which shall become the property of the Government. Following the periods of steam curing, the pipe shall be protected from rapid drops in temperature which may damage the pipe. (b) Water curing.-Concrete in pipe may be water cured by covering with water-saturated material or by a system klers, porous hose, or by any other apof perforated pipes, mechanical sprin proved method which will keep the inside and outside continuously wet during the specified curing period. * g. Reinforcement. (1) Circumferential reinforcement. The circumferential reinforcement shall be a single-cage circular, double-cage circular, or elliptical cage as shown in Table 1. Elliptical reinforcement will be permitted for 25- and 50-foot head classes only and only in pipe 18 to 72 inches in diameter, inclusive. All pipe with a wall thickness less than 314 inches shall be reinforced with a single-circular cage of steel and all pipe with wall thicknesses of 314 inches and more shall be reinforced with two separated cages of steel, except that elliptical cages will be accepted as provided above. The areas of circumferential reinforcement shown in Table 1 are the minimum requirement for each of February 7, 1973 the nominal wall thicknesses shown ring shall not be less than one-half in the table. inch nor more than 1 inch from the end of the pipe unit. (2) Longitudinal In the event the pipe manufacturer furnishes pipe with a nominal wall thickness between the wall thicknesses shown in Table 1 for that size of pipe, the minimum required steel area for single-circular or elliptical cage or for inner and outer cage circular steel shall be computed as a straight-line variation between the two steel areas shown in the table for the corresponding steel arrangement. Where single-cage circular reinforcement is used, it shall be placed from 35 to 50 percent of the wall thickness from the inner surface of the pipe: Provided, That the minimum concrete cover specified below shall be maintained. Where two separated circular cages of reinforcement are used, the inner and outer cages shall be placed so that the concrete cover, measured radially, over the circumferential reinforcement will be as follows: rein force ment. Each layer of circumferential reinforcement shall be assembled into a rigid cage supported by longitudinal bars which extend the full length of the pipe. The minimum concrete cover for circumferential steel given in Subparagraph (1) above shall also apply to placement of longitudinal bars except that the longitudinal bars or rods. may extend to either or both ends. of the pipe unit to form supports for holding the circumferential cage in proper position. Not less than four longitudinal bars at approximately equal spacing shall be provided for each cage, and additional bars shall be provided as necessary so that the circumferential spacing between longitudinal bars shall not exceed 42 inches in any cage. The contractor shall also provide such additional longitudinal steel as may be necessary to prevent the occurrence of circumferential cracking in the pipe wall and to provide sufficient rigidity to the cage. Where the pipe joint construction requires the use of a bell, the minimum number of longitudinal bars shall be provided in the bell and may be continuous bars or spliced to the main longitudinal bars. The circumferential bars of each cage shall be spaced and supported by welding or tying each hoop to the longitudinal bars. Spacer bars, chairs, or other methods shall be provided to maintain the reinforcement cage or cages (c) Concrete bell and spigot with single rubber gasket (Type R-3) as shown on Drawing No. 151 (40-D-5806) or 152 (40-D-5807). (d) Concrete bell and spigot with single rubber gasket (Type R-4) as shown on Drawing No. 153 (40-D-3808) or 154 (40-D-5809). * (3) Laps, welds, and spacing.If the splices are not welded, the reinforcement shall be lapped not less than 20 diameters for deformed bars, and 40 diameters for plain bars or cold-drawn wire. If welded, the member at either a welded splice or intersection shall develop a tensile strength not less than 52,500 pounds per square inch as determined by weld test specimens. The spacing center to center of adjacent airholes, chipped or spalled concrete, rings of circumferential reinforcement in a cage shall not exceed 4 inches. h. Joints. (1) Joints, general.-The joint assemblies shall be so formed and accurately manufactured that when the pipes are drawn together in the trenches, the pipe shall form a continuous watertight conduit with smooth and uniform interior surface, and shall provide for slight movements of any pipe in the pipeline due to expansion, contraction, settlement, or lateral displacement. The rubber gasket shall be the sole element of the joint depended upon to provide watertightness. The ends of the pipe shall be in planes at right angles to the longitudinal centerline of the pipe, except where bevel-end pipe for deflections up to 5° is specified or indicated for bends. The ends shall be finished to regular smooth surfaces. The ac (4) (g) The surfaces of the bell and spigot in contact with the gasket, and adjacent surfaces that may come in contact with the gasket within a joint movement range of three-fourths inch, shall be free from laitance, or other defects, except that individual airholes may be repaired as provided in Subparagraph j. (2). i. Physcial test requirements. (1) General testing requirements. -All pipe units and test cylinders for purpose of tests shall be furnished by the contractor at no cost to the Government: Provided, That pipe units which satisfactorily pass testing procedures may be used for installation in pipelines and structures. The contractor shall provide at his expense adequate equipment, and all labor and materials for making the tests on pipe units. The strength of concrete and the acceptability of pipe will be determined by tests of the compressive strength of the concrete used in the pipe as provided in Subparagraphs e.(1) and e. (4), by examination of the quality, amount, and accuracy of placement February 7, 1973 of the reinforcement, and by hydrostatic pressure tests. Tests on the various pipe sizes, as provided above, shall be made on pipe manufactured in each test period of consecutive working days as follows: (a) Hydrostatic pressure tests on 1 percent, but not less than one pipe unit, of each size and class of pipe. (b) Hydrostatic joint tests on one-half percent, but not less than one joint, for each size and class of pipe. For the purposes of testing the pipe units, the length of the test period will be set at the number of days the plant of the pipe manufacturer is normally operated in a calendar week. The test period will include any shutdown of the pipe manufacturer's plant, which does not exceed a 24-hour period, due to failure of the plant or equipment. The length of the test period may be reduced at the discretion of the contracting officer if there is a significant change in the materials used in the pipe, in the mix proportions, or in production procedures or by numerous shutdowns of the pipe manufacturer's plant due to failures of the plant or equipment. The length of the test period may be increased at the discretion of the contracting officer when results of tests for successive periods indicate that the contractor's operations are productive of uniformly acceptable pipe. In the event that a pipe unit fails to withstand the required tests, the contractor shall have the right to test two other units of the pipe selected by the contracting officer from the same test period's run from which the original was selected. If these two pipe units successfully pass the test, the remainder of the pipe in that test period's run will be accepted. If either of these pipe units fail, then the remainder of the test period's run will not be accepted until each pipe unit has satisfactorily passed the tests. (2) Hydrostatic test on pipe units.-Hydrostatic tests the on pipe units shall be made by applying suitable bulkheads at each end of the pipe and filling the pipe with water. Before the test pressure is applied the pipe shall be allowed to stand under a pressure of 10 pounds per square inch for at least 3 hours. Acceptance hydrostatic tests shall be made to 120 percent of the specified internal pressure of the pipe class for which it is designed. The pipe shall withstand the test pressure prescribed above for at least 20 minutes without cracking and with no leakage appearing on the exterior surface. Moisture appearing on the surface of the pipe in the form of patches, or beads adhering to the surface will not be considered as leakage. Slow forming beads of water that result in minor dripping which can be proved to seal and dry up within 1 week while under the prescribed test pressure will be considered acceptable. (3) Hydrostatic test of rubber gasket-type joints. Hydrostatic pressure tests of rubber gasket-type joints shall be made on joints assembled of two units of pipe, properly connected in accordance with the joint design. Suitable bulkheads may be provided within the pipe adjacent to and on either side of the joint, or the manufacturer may bulkhead the outer ends of the two joined pipe units and conduct hydrostatic tests on both the pipe and the pipe joint concurrently. No mortar or concrete coatings, fillings, or backings shall be placed prior to joint watertightness tests. After the pipe units are fitted together with the rubber gasket or gaskets in place, the watertightness of the joints shall be tested under hydrostatic heads of 120 percent of the pressure for which the pipe is designed, and there shall be no water leakage through the rubber gasket joint. j. Miscellaneous Requirements.(1) Sizes and permissible variations. Variations of the internal diameter shall not exceed plus or minus 1.50 percent for pipe having an internal diameter of 12 to 24 inches, inclusive; 1 percent for pipe 27 to 36 inches, inclusive; and 0.75 percent for 39-inch diameter and larger: Provided. That in not more than 10 percent of the pipe units of any one size to be installed in one continuous reach of pipeline, up to two times the above-listed permissible variations will be accepted if such variation does not extend more than one-fourth of the length of the pipe unit. Within this distance the net area of the pipe opening shall (2) Finish.-Pipe shall have cylindrical interior surfaces and shall be free from fractures, excessive interior surface crazing, and roughness. The interior and exterior surfaces shall be concentric at any normal cross section of pipe. Pipe manufactured by pouring and vibrating methods within stationary inside and outside forms shall have smooth glossy surfaces, relatively free from pits and air holes. Pipe manufactured by a centrifugal spinning method shall be free from excessive brush marks, that indicate hard brushing of the interior surface for the removal of water and laitance, and which will markedly affect the water-carrying capacity of the finished pipeline. Float rock or other light materials such as clay balls or wood particles appearing on the inside surface of the pipe will be cause for rejection. Individual air holes in gasket bearing areas of precast-concrete pipe may be filled with a handplaced, stiff, preshrunk 1:1 mortar of cement and fine sand with no other preparation than thorough |